-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 170812
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
412 AM EDT FRI MAY 17 2013

.SYNOPSIS...
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AN UPPER DISTURBANCE WILL MOVE NORTH OF THE AREA THROUGH THE WEEKEND
AS ATLANTIC HIGH PRESSURE BUILDS ACROSS THE REGION. HIGH PRESSURE
WILL BE THE DOMINANT FEATURE THROUGH MUCH OF NEXT WEEK BEFORE A COLD
FRONT POSSIBLY APPROACHES ON FRIDAY.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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PRE-DAWN...IT HAS BEEN A MILD AND MORE HUMID OVERNIGHT ACROSS THE
REGION AS SURFACE TEMPS AND DEW POINTS BOTH SOLIDLY UP IN THE 60S.
THE LOW LEVEL RIDGE AXIS CONTINUES TO POKE INTO N FLORIDA AND FAR
S GEORGIA WITH A WEAK PRES PATTERN FOR THE AREA. OVERNIGHT WE HAVE
SEEN PERIODS OF HIGH CLOUDS AT TIMES...OTHERWISE IT HAS BEEN MOSTLY
CLEAR.

TODAY...THE MOST NOTABLE FEATURE ON WATER VAPOR SATELLITE IMAGERY
IS THE SLOW MOVING CUT-OFF MID LEVEL LOW OVER THE MID SOUTH REGION.
THIS FEATURE IS FORECAST TO OPEN UP AND LIFT ENE INTO THE TENNESSEE
VALLEY REGION WELL TO OUR NW. A WEAK MID LEVEL SHORT WAVE IS
EXPECTED TO RIPPLE THROUGH GEORGIA TODAY BUT IN THE LOW LEVELS THE
ATLC RIDGE REMAINS IN CONTROL.

MODELS ARE SPLIT ON WHETHER ISOLATED LATE DAY CONVECTION WILL INITIATE
TO THE W OF I-95 TODAY. GLANCES AT MODIFIED PROXIMITY NAM/GFS SOUNDINGS
AT KOGB-KAGS-KAYS INDICATE PRETTY POOR VERTICAL PROFILES FOR DEEP
CONVECTION POTENTIAL. THERE IS SOME MID LEVEL INSTABILITY NOTED...LIKELY
TO BE NEGATED BY ANY FOCUS IN LOW LEVEL THETA-E ADVECTION AND MARGINAL
SURFACE DEW POINTS. WE HELD ONTO 15-17 PERCENT POPS MAINLY W OF I-95
PER PERSISTENCE AND VARIOUS HIGH RESOLUTION GUIDANCE TRENDS. WE ARE
NOT LOOKING FOR MUCH IN THE WAY OF DEEP OR SUBSTANTIAL CONVECTION...
PERHAPS A FEW SPOTTY CELLS ALONG THE LATE AFTERNOON SEA BREEZE
INTRUSION. NO RAIN EXPECTED IN EITHER CHARLESTON OR SAVANNAH.

MODEL CLOUD PROGS AND SOUNDINGS INDICATE WE WILL SEE MORE SUNSHINE
TODAY AND HIGHS BETWEEN 85 AND 90 DEGREES ARE LIKELY. SURFACE WINDS
MOSTLY LIGHT TODAY OUTSIDE OF ANY SEA BREEZE OSCILLATION EFFECTS
NEAR THE COAST.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
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DRY WEATHER ANTICIPATED TONIGHT WITH A SHORT WAVE RIDGE BUILDING
ACROSS GEORGIA AND THE CAROLINAS. OCCASIONAL MID/HIGH CLOUDS WILL
PASS THROUGH THE REGION WITH LOWS IN THE 60S...SIMILAR TO READINGS
ON FRI MORNING.

AN UPPER SHORTWAVE WILL DRIFT SOUTHEAST FROM THE OHIO VALLEY INTO
NORTH CAROLINA SATURDAY THROUGH MONDAY. ALTHOUGH THE BRUNT OF THE
VORTICITY WILL STAY NORTH OF THE FORECAST AREA...THE UPPER HEIGHT
FALLS WILL PRODUCE A MORE FAVORABLE ENVIRONMENT FOR SHOWERS AND
THUNDERSTORMS. LOW-LEVEL MOISTURE WILL INCREASE SUBSTANTIALLY SUNDAY
INTO MONDAY WHEN THE UPPER VORT MAKES ITS CLOSEST APPROACH. ON
SATURDAY THE SEABREEZE SHOULD BE THE PRIMARY DRIVER FOR CONVECTION.
SUNDAY INTO MONDAY THE COVERAGE SHOULD BE A BIT GREATER AS
MID-LEVELS COOL SLIGHTLY IN CONCERT WITH INCREASING LOW-LEVEL
MOISTURE. WE HAVE 30-40 POPS BOTH DAYS...WITH SLIGHT CHANCES DURING
THE OVERNIGHT HOURS. HIGH TEMPS WILL BE SOLIDLY IN THE 80S WITH LOWS
IN THE 60S.
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&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
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THE UPPER SHORTWAVE NORTH OF THE AREA ON MONDAY WILL ESSENTIALLY
DISSOLVE ACROSS THE EASTERN CAROLINAS ON TUESDAY LEAVING A VERY WEAK
RIDGE PATTERN IN PLACE. ATLANTIC HIGH PRESSURE WILL PRODUCE AN
ONSHORE FLOW WITH SEA BREEZES DEVELOPING EACH AFTERNOON. SURFACE
DEWPOINTS WILL PERSIST IN THE MIDDLE 60S WITH HIGHS CLIMBING WELL
INTO THE 80S EACH DAY. ALTHOUGH THERE ARE NO STRONG FORCING
MECHANISMS...WE KEPT ISOLATED SHOWERS AND THUNDERSTORMS IN THE
FORECAST EACH AFTERNOON/EVENING. A COLD FRONT COULD MOVE INTO THE
AREA ON FRIDAY.
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&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 06Z SATURDAY.

EXTENDED AVIATION OUTLOOK...PRIMARILY VFR. ISOLATED TO SCATTERED
AFTERNOON SHOWERS/THUNDERSTORMS EXPECTED EACH AFTERNOON THROUGH
EARLY NEXT WEEK.

&&

.MARINE...
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THROUGH TONIGHT...THE LOW LEVEL RIDGE AXIS REMAINS CONSTANT AND
SO DOES OUR FORECAST WITH A SOUTHERLY COMPONENT LESS THAN 15 KT
AND SEAS 3 FT OR LESS. DIRECTIONS SHOULD BACK A BIT MORE SE ALONG
THE GEORGIA COAST THIS AFTERNOON AS THE LAND WARMS AND THE SEA
BREEZE PUSHES INLAND.

ATLANTIC HIGH PRESSURE WILL BE THE PRIMARY MARINE INFLUENCE THROUGH
THE PERIOD WITH SOUTHERLY FLOW PREVAILING. WIND SPEEDS WILL PERSIST
IN THE 10-15 KT RANGE WITH SEAS 4 FT OR LESS.
-- End Changed Discussion --

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.

&&

$$

SYNOPSIS...
NEAR TERM...
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...
MARINE...JRL